You're full of crap. The LB9 (TPI 305) was exactly the same regardless of which trim level it was put in.

And there were no L98 (TPI 350) Z28s until the IROC was a Daytona.

 

According to the fellows here and some research I did the Irocs were just a trim package and a nicer suspension. i dont know where you got that manual but you are reading it wrong or something here is a list of specs, for example the 85 Iroc and Z28 tpi's both put out 215hp @4400rpm. It is a common misconception that the Iroc sticker adds hp and as we all know only stickers on ricers can do that.

http://www.phy.duke.edu/~hartley/iroc/iroc_specs.html

 

i just scanned a pgae out of a chiltons book. i couldnt find the book i looked at before but if you wanna see it i have to email it to you cuz my computer wont let me do anything with it on the internet for some reason. it is a weird book cuz i marked a part that said the 85-87 F 305 TPI has 265hp @4400 and 275tq @3200. i dont beleive it now but a few years ago before i knew much about these carsi thought it was true. i dont know why they would put those numbers down to begin with.
if you want gimme an email and i can send it to you.

 

http://www.thirdgen.org/1987-chevy-camaro
^Just to clear up some discrepancies, there WAS different power ratings for the LB9. However, using 87 as an example, you can see that it has nothing to do with the trim level, rather the transmission. The T-5's got 25 more horsepower (190 vs 215) @ 4400 RPM over 4000.

 

I wonder how much hp that 400 rpms make up for? 190@4000 vs 215@4400 probably not that much but neither is 15hp. I wonder why they chose to go with dif rpms by comparison. Good to see you cleared some of that up but the engines are still the same, one is not stronger than the other. It is a common misconception that just bc you have an Iroc you have a faster car (I know I thought so) and I know some people that think all Irocs have 350s in them. That is still way off from that page he mentioned that has 265@4400

 

The h.p. to rpm rating isn't some arbitrary number that they pull out of a hat. Every engine hits it's peak h.p. at a certain rpm. Take the one that is rated at 215 h.p. @ 4400 rpm for example. That means it hits peak hp (215) at 4400 rpm, and then hp starts to drop after 4400 rpm. Engines hit peak hp at different rpm's for different reasons, such as the profile of the cam, type of induction, flow capacity of the heads, etc.

 

I honestly didnt know how that worked so thanks. It is simple and should be common sense when you think about it. I feel kinda stupid now, thanks alot

 

Alot of ppl forget irocs come with borg and warner posi/limited slip rears not gm axles

 

Not sure if reg z28's have rear disc brakes not having borg n warners also w that paticular brake system gets a proportioning valve not to mention cus i had to research comp controlled custom shift points unique to irocs not same as vettes but don't think its shared by 28's either...

 

for the reason I just bought and restored a 5.7 iroc with b-w axles w rear disc brakes also comes with custom engineered offset iroc rims that r close to impossible to replace cus chevy the dealer wheel shops and even most classic parts suppliers cannot find the real offset specs or do not sell properly offset iroc rims front wheels r not interchangable with rears...